Prince William and Prince Harry will join King Charles III and other members of the royal family to walk behind the coffin during the procession.
The coffin will be carried in a hearse, and once it arrives, a short service will be held by the Archbishop of Canterbury.
The Queen’s coffin will lie in Westminster Hall, the heart of Britain’s parliament, until her funeral on Monday.
From Wednesday afternoon, citizens will have the opportunity to pass by the coffin, which will be on a raised platform or on a catafalque. Thousands are expected to line the streets of the capital, with some staying overnight to pay their respects.
Harry joining the procession on Wednesday is the latest in a series of appearances with William since the Queen’s death, as the brothers have sought a show of unity despite tensions in recent years since Harry stepped down as king.
The joint appearance of William and Harry and their wives Catherine, Princess of Wales and Meghan, Duchess of Sussex in Windsor on Saturday was a surprise and was not announced in advance. William invited the Sussexes along for the ride to see the memorabilia left for the Queen and greet them, a source told CNN.
The Queen’s coffin was taken from Balmoral Castle to Edinburgh on Sunday. The six-hour drive marked the first leg of the late monarch’s eight-day journey to her final resting place.
Monday evening in Edinburgh St. Mourners lined up outside Giles Cathedral to pay their last respects. The Scottish Government said more than 26,000 people managed to get past the Queen.
On Tuesday, the Queen’s coffin was taken to St. Giles Cathedral to Buckingham Palace in London.
He was taken from the cathedral to Edinburgh Airport in a coach before being flown to RAF Northolt air base in west London in a C-17 Globemaster transport plane.
The coffin was then taken to Buckingham Palace, where it was received by the Queen’s family and laid to rest overnight in the Bow Room.